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Is it parallel feed on not?
http://www.dcaudiodiy.com/phpBB3/viewtopic.php?f=5&t=441		 Page 1 of 2
Author:  Roscoe Primrose [ February 10th, 2014, 2:30 pm ]
Post subject:  Is it parallel feed on not?
At : http://www.nutshellhifi.com/library/Rosetta_Stone.html Lynn Olson claims that the output stage for the WE 32A amplifier is parallel feed. Looking at the schematic included in the article, it's pretty clear to me that it is, in fact, NOT parallel feed, but standard plate loading transformer with the DC going though the transformer primary. I've sent Lynn a couple of emails, with no response, and no correction of the page....

I'm including the image with the schematic here to help with the discussion...

Image

Thoughts?

Roscoe
Author:  FerdinandII [ February 10th, 2014, 4:28 pm ]
Post subject:  Re: Is it parallel feed on not?
Nope.

Pin 6 on the output transformer Primary goes nowhere but the the plate.
The 1k-ohm cathode bias resistor goes from the center tap of the directly heated cathode transformer winding to ground.

There is a RC feedback circuit to the bottom of the input transformer secondary, but it isn't anything like a parallel feed.
Besides, WHERE'S THE PARAFEED CHOKE...????

No CAP to break the AC and DC loops, and no separate chocke for the AC load?

Nope, not parallel feed, IMHO.

Of course, I could be wrong..........
Author:  Roscoe Primrose [ February 11th, 2014, 12:57 am ]
Post subject:  Re: Is it parallel feed on not?
FerdinandII wrote:
There is a RC feedback circuit to the bottom of the input transformer secondary, but it isn't anything like a parallel feed.


The "retard coil" and the 2 2uF caps are a simple CLC power supply filter. The second cap is returned to the top of the cathode bias resistor, which eliminates the need for a cathode bypass cap, and also introduces some hum cancellation....

My 300B amps use this basic circuit, although I haven't played with the second PS cap to find the value that gives minimum hum....

Roscoe
Author:  FerdinandII [ February 11th, 2014, 11:40 am ]
Post subject:  Re: Is it parallel feed on not?
I was referencing the .5mF cap and the 48k resistor on pin 3 of the input transformer. Looks like feedback to me...... :think:

Roscoe Primrose wrote:
FerdinandII wrote:
There is a RC feedback circuit to the bottom of the input transformer secondary, but it isn't anything like a parallel feed.


The "retard coil" and the 2 2uF caps are a simple CLC power supply filter. The second cap is returned to the top of the cathode bias resistor, which eliminates the need for a cathode bypass cap, and also introduces some hum cancellation....

My 300B amps use this basic circuit, although I haven't played with the second PS cap to find the value that gives minimum hum....

Roscoe
Author:  Roscoe Primrose [ February 11th, 2014, 11:46 am ]
Post subject:  Re: Is it parallel feed on not?
FerdinandII wrote:
I was referencing the .5mF cap and the 48k resistor on pin 3 of the input transformer. Looks like feedback to me...... :think:


No, just coupling. The .5mf cap is the AC coupling for the input transformer secondary, the 48k resistor provides a dc connection to ground for the 205D grid bias.

Roscoe
Author:  Roscoe Primrose [ February 12th, 2014, 4:36 pm ]
Post subject:  Re: Is it parallel feed on not?
Kinda surprised there hasn't been more discussion in this thread...
Author:  Stuart Polansky [ February 12th, 2014, 5:29 pm ]
Post subject:  Re: Is it parallel feed on not?
PPTTFMF!

:auto-layrubber:
Author:  Jetbat [ February 12th, 2014, 6:04 pm ]
Post subject:  Re: Is it parallel feed on not?
Yes in a way. It is parallel feeding the tube through the grid and cathode.

Scott
Author:  Roscoe Primrose [ February 12th, 2014, 7:00 pm ]
Post subject:  Re: Is it parallel feed on not?
Stuart Polansky wrote:
PPTTFMF!


Huh? :confusion-confused:
Author:  Stuart Polansky [ February 12th, 2014, 7:43 pm ]
Post subject:  Re: Is it parallel feed on not?
From another board I post on, cylinder head wars. Each abbreviated proclamation is part cheering and part assertion. For instance, EHTTFMF means Edelbrock Heads To The Front My Friend. Okay, so maybe it's not "my friend". Still......Push Pull To The Front......

See, it was supposed to be a slice of humor.

Oh well...
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